Lactose a. Determine from the data below whether lactonase is behaving according
ID: 1053888 • Letter: L
Question
Lactose
a. Determine from the data below whether lactonase is behaving according to Michaelis- Menten kinetics and estimate the Km and Vmax for uninhibited lactonase with its favored substrate, glucose.
b. Determine the Km, and Vmax for the uninhibited enzyme with lactose as substrate if the enzyme is present at a concentration of 10 pM.
c. Identify what type of reversible inhibition is exhibited by the inhibitor in this experiment.
no inhib inhib present present present present [S] (mM) Vo (mM/min) Vo (mM/min) Vo (mM/min) Vo (mM/min) Vo (mM/min) 0.2 mM 0.6 mM 1.8mM 5.4mM 1 22 19 16 13 9 2 34 30 26 22 15 3 43 40 34 27 20 4 50 45 39 33 25 5 54 50 44 37 28 6 57 53 47 40 30 7 60 56 49 42 32 8 62 58 51 43 34 9 64 60 53 44 35 10 65 61 54 45 36Explanation / Answer
if the data were to obey Michelis- Menten kinetics
the equation is 1/V= (KM/Vmax)*1/S + 1/Vmax
so a plot of 1/V vs 1/S should give a straight line for the equation to be obeyed. the plots shown are obeying the equation
for uninh ibited enzyme, 1/Vmax =0.0179
Vmax = 1/0.0179=55.86 mM/min
KM/Vmax = 0.0939
KM= 55.86*0.0939=5.24 mM
b) i0.2mM inhibitor, Vmax =1/0.0154=64.93 and KM/max = 0.0613 and KM= 64.93*0.613=3.98M
uncompetitive inhibition since KM has decreased
the trend is similar in other cases as well.
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